1. Field of the Invention
The invention relates generally to the field of photography and more particularly to a viewfinder for indicating substantially how much of a subject an objective lens projects on to the film in a camera.
2. Description of the Prior Art
When taking a picture it is necessary to know not only in what direction to aim the camera but also how much of the subject will be included in the picture. For this reason practically every camera has as viewfinder of some kind.
A viewfinder known as a "frame finder" is one of the simplest types of viewfinders. Typically, the frame finder consists of a front frame and a small rear peep-sight, each of which corresponds in shape to the negative. The frame is mounted on or built into the camera above the objective lens and in the same plane as the lens, and the peep-sight is mounted on or built into the camera in the same plane as the film. The viewing axis of the frame and peep-sight is parallel to the optical axis of the lens.
When the eye is brought close to the aperture of the rear peep-sight, the view bounded by the front frame is almost exactly the same as the taking field of the objective lens. Therefore, one can see the portion of the subject the lens projects on to the film. The only error is that of parallex, which is more or less negligible for a subject beyond about six feet. Apart from this, the view through the peep-sight and the frame will be substantially coincident with the portion of the subject recorded on the film.
When using the frame finder it may be difficult for one to obtain an accurate view of the portion of the subject to be recorded on the film. If the eye is not centered with respect to the rear peep sight, the view through the front frame will appear hazy or obscure. However, one may find it difficult to know exactly when the eye is centered with respect to the peep sight. Hence, the user may not take a picture of what he or she intended.